Plasma, erythrocyte and urinary selenium levels were determined in 21 sickle cell homozygote patients, 20 siblings with sickle cell traits, 29 parents and in 21 healthy controls with an HbAA pattern. The mean levels of plasma and erythrocyte selenium and the daily urinary selenium depletion were found to be lower in the HbSS patients than in the controls (p < 0.02; p < 0.001; p < 0.001, respectively). Urinary selenium depletion was found to be lower in the sickle cell trait siblings than in the controls (p < 0.001), but the plasma and erythrocyte selenium levels were close to normal values (p > 0.05). The mean erythrocyte selenium levels were found to be decreased in the parents as compared with the controls (p < 0.05), which indicates that urinary selenium losses may be replenished primarily by sources in the plasma and in the erythrocytes before stores in the other parts of the body are used.